The major goal of the research plan to be pursued is to determine the relationship of certain lymphocyte cell surface molecules to immunodeficiency disease states such as AIDS. There are three main aims: a) to evaluate the genetic polymorphism of the human CD4 and CD8 molecules in a broad based population (b) to determine if polymorphisms in either CD4 or CD8 are related to either susceptibility to HIV infection progression of disease (c) to determine if there is a correlation between the genetic structure of CD4 and CD8 and primary immunodeficiency diseases with T cell abnormalities. Methods to be used include population studies, DNA sequencing, polymerase chain reaction, molecular genetic cloning techniques, family studies, and patient evaluations.